The 3D printer is one type of rapid prototyping, and it is a three-dimensional printer for modeling a three-dimensional object based on 3D data such as 3D CAD and 3D CG. Systems of 3D printing have been known, such as a fused deposition modeling system (hereinafter referred to as an FDM system), an inkjet ultraviolet curing system, a stereolithography system, and a selective laser sintering system. Among these systems, the FDM system is a modeling system of heat-melting, extruding, and laminating polymer filaments to obtain a three-dimensional object, and the FDM system does not use a reaction of the material unlike other systems. Accordingly, a 3D printer of an FDM system is small and inexpensive, and has become popular in recent years as an apparatus with less post-processing. In order to model a three-dimensional object having a more complex shape in a FDM system, a modeling material constituting the three-dimensional object and a support material for supporting a three-dimensional structure of the modeling material are laminated to obtain a precursor of the three-dimensional object, and then the support material is removed from the precursor of the three-dimensional object to obtain the target three-dimensional object.
An example of the method of removing the support material from the precursor of the three-dimensional object is a method of using a methacrylic acid copolymer as the support material and soaking the precursor of the three-dimensional object in an aqueous strong alkaline solution to remove the support material (for example, JP-T-2008-507619). The methodutilizes that carboxylic acid in the methacrylic acid copolymer is neutralized by an alkali and dissolved in an aqueous strong alkaline solution.